We challenge the prevailing view that pure informational lobbying (in the absence of political contributions and evidence distortion or withholding) leads to better informed policymaking. In the absence of lobbying, the policymaker may prioritize the more-important or ex ante morepromising issues. Recognizing this, interest groups involved with other issues can have an incentive to lobby, in order to change the issues that the policymaker learns about and prioritize. We identify two channels through which informational lobbying is detrimental, in the sense of leading to worse policy and possibly less-informed policy choices. First, it can cause the policymaker to give priority to less important issues with active lobbies, rather than the issues that are more-important to his constituents. Second, lobbying by interest groups on issues with ex ante less-promising reforms may crowd out information collection by the policymaker on issues with more-promising reforms. The analysis fully characterizes the set of detrimental lobbying equilibria under two alternative types of issue asymmetry.